Source Code Scanners for Better Code

They aren't a replacement for manual checks and edits, but tools like Flawfinder, RATS and ITS4 can point you in the right direction.

Coding is tough enough, and coding right
can sometimes seem an almost impossible task. Between design
constraints, deadlines and making it work in the first place, it's
difficult to get your code secure. Security concerns, however, can
be helped by scanners.

Source code scanners are nothing new. Tools like
lint have been around for many,
many years to help you find errors in your C code. There are even
lint checkers for DNS and HTML files,
nslint and
weblint, respectively. The lint
tool doesn't explicitly talk about insecure code, though, only
basic inconsistencies in your style.

Source code audits are also great things, things like the
Linux Auditing Project. However, audits can take a lot of time and
money if you outsource them, though the payback is well worth the
investment. Source code scanners used available for only commercial
software, prohibiting their use by many Linux developers and
researchers, who didn't always place user friendliness high on
their lists of goals.

A couple of years ago, pscan
was released under the GPL. It's a simple format string scanner but
one of the first such tools commonly available on the hobbyist
developer market. Since then, three new source code scanners have
become available for source available software, and all three are
worth looking at. Not all of them are open source, but they do work
well for most users coding in C or C++.

The resources listed at the end of this article are worth
checking out. The Open Source Quality Project has links to several
sites, including commercial products and academic research groups,
involved in performing software quality testing. Some of these
tools can do more rigorous testing but can be far less
user-friendly.

Flawfinder

Developed by the noted author and coder David Wheeler,
Flawfinder is a Python program that can be used to assist auditing
C and C++ code. It's in the early stages, currently at version
0.19, but already it's strong competition for the other tools
listed here in the 1.x stages. Flawfinder is also quite fast,
covering thousands of lines of C code on a typical desktop machine
in a matter of seconds. Flawfinder is released under GPL version 2,
meaning it is free software.

Flawfinder also shows some intelligence when it comes to
scanning for vulnerabilities. For example, in tests using
intentionally insecure code, Flawfinder was able to distinguish
between strcpy() from a constant sized string and variable length
strings and tell the difference between vulnerabilities and false
hits. Furthermore, Flawfinder understands the gettext libraries and
their use in internationalization.

RATS

RATS, the Rough Auditing Tool for Security, is a source code
scanner under active development that is capable of scanning C,
C++, Perl, PHP and Python source code. Also released under the GPL,
some of the RATS developers also worked on a similar tool, ITS4
(discussed below). The current version, 1.3, is noticeably more
stable than version 1.2, but it still can fail on large amounts of
input.

RATS is configurable when the source code is modified
(through lexical analysis), with error messages controlled by XML
reporting filters, which requires the XML tool
expat to also be installed. At
runtime, you can configure the level of output you wish to see
(defaulting to medium), alternative vulnerability databases and
even report functions that accept input from the user, facilitating
the tracking of user supplied data.

Some of the specific limitations of RATS include the use of
greedy pattern matchings, meaning that tracking for "printf" will
match not only "print()" calls but also "vsnprintf()" and the like.
This can make it difficult to filter hits from noise when specific
functions are being sought with the -a flag.

The authors of RATS and Flawfinder, by the way, plan to
coordinate their development efforts to produce a high quality,
open-source development tool. This should be good to watch, as each
development team is well respected in the field.

ITS4

One of the original source available scanners for Linux and
UN*X, It's the Software Stupid Source Scanner (ITS4), scans C and
C++ source for common security-related flaws. Developed by Cigital
(then known as RST Technologies) and some of the same people who
went on to develop RATS, ITS4 has set the pace. Many of the
niceties in ITS4 are also available in RATS or Flawfinder, such as
ignorable lines, tracking user input (the -m flag) and alternative
databases.

Modification of a particular project or site is relatively
straightforward. A simple text file of vulnerabilities is used,
which can be added to or modified to suit any specifics of a
system. It should be noted that ITS4 comes with a non-free license,
even though the source is available. Users should read and
understand the license if they are doing anything beyond hobbyist
programming with it.

You have a good overview of the 3 source code scanners, are these the commonly used one's, are there any other.
I had a quick question on source code scanners, Can this scanners be used to scan code written for different platforms?(i.e. me running source code scanner on linux, can i scan some piece of code written to run on Windows, Unix)